little starfish ???

Question
Not sure who to ask cause we are just starting out on saltwater..We have a 24gal. tank that we got with coral,  live rock,and 4 fish..My question is, there are ,what looks like little starfish on the glass about a dozen..What are they..Hope I explained it well enough..
Thank You
Linda

Answer
Hi Linda. There are a few different kinds of small starfish that hitch hike into a tank on live rock. Most commonly found are the small brittle starfish. These are typically very small not even an inch in length. They are commonly found in crevices and holes in rocks with just an arm or two sticking out. They are tan or white with dark bands on the legs. Their bodies are also tan to white with a darker spot in the middle. These are not typically found on the glass but can be seen occasionally creeping along the bottom. These are completely harmless and are very beneficial to your tank because they eat small particulate matter and detritus in places that you cannot reach. The second species commonly found in a reef tank are those called asterina. These starfish are small tan, grey or brownish starfish often with uneven legs. They are harmless herbivores and can reproduce by dropping a leg off and thus a whole new starfish may grow from that arm. There is allot of controversy on these starfish. Some say they eat coral polyps while others have them by the hundreds in their tank and have never had a problem with them. Most likely there are variations with in this species that have different feeding habits. On one hand they can be completely harmless and actually beneficial at cleaning up algae and detritus from your tank. On the other hand there is always the possibility that they are the ones that eat corals. There is no accurate way to tell the difference between the reef safe kind and the non reef safe ones. The only way to tell is by observing them in your tank. If you have as many of them as you do and no coral polyps have gone missing then it is safe to assume that the ones you have are reef safe and actually beneficial. If you have noticed some polyps completely disappearing during the period of darkness in your tank then you may want to remove them.
If the starfish you have do not sound like either of these you can always get back to me with a better description and I can try to assist you further.